package name.huzhenbo.java.enums;

/**
 * Effective Java, Item 34: emulate extensible enums with interfaces.
 * <p/>
 * In summary, while you cannot write an extensible enum type, you can
 * emulate it by writing an interface to go with a basic enum type that imple-
 * ments the interface. This allows clients to write their own enums that implement
 * the interface. These enums can then be used wherever the basic enum type can be
 * used, assuming APIs are written in terms of the interface.
 */
interface IOperation {
    double apply(double x, double y);
}
